Bag-in-containers, also referred to as bag-in-bottles or bag-in-boxes depending on the geometry of the outer vessel, all terms considered herein as being comprised within the meaning of the term bag-in-container, are a family of liquid dispensing packaging consisting of an outer container comprising an opening to the atmosphere—the mouth—and which contains a collapsible inner bag joined to said container and opening to the atmosphere at the region of said mouth. The system must comprise at least one vent fluidly connecting the atmosphere to the region between the inner bag and the outer container in order to control the pressure in said region to squeeze the inner bag and thus dispense the liquid contained therein.
Traditionally, bag-in-containers were—and still are—produced by independently producing an inner bag provided with a specific neck closure assembly and a structural container (usually in the form of a bottle). The bag is inserted into the fully formed bottle opening and fixed thereto by means of the neck closure assembly, which comprises one opening to the interior of the bag and vents fluidly connecting the space between bag and bottle to the atmosphere; examples of such constructions can be found inter alia in U.S. Pat. Nos. 3,484,011, 3,450,254, 4,330,066, and 4,892,230. These types of bag-in-containers have the advantage of being reusable, but they are very expensive and labour-intensive to produce.
More recent developments focused on the production of “integrally blow-moulded bag-in-containers” thus avoiding the labour-intensive step of assembling the bag into the container, by blow-moulding a polymeric multilayer preform into a container comprising an inner layer and an outer layer, such that the adhesion between the inner and the outer layers of the thus produced container is sufficiently weak to readily delaminate upon introduction of a gas at the interface. The “inner layer” and “outer layer” may each consist of a single layer or a plurality of layers, but can in any case readily be identified, at least upon delamination. Said technology involves many challenges and many alternative solutions were proposed.
The multilayer preform may be extruded or injection moulded (cf. U.S. Pat. No. 6,238,201, JPA10128833, JPA11010719, JPA9208688, U.S. Pat. No. 6,649,121). When the former method is advantageous in terms of productivity, the latter is preferable when wall thickness accuracy is required, typically in containers for dispensing beverage.
Preforms for the production of integrally blow-moulded bag-in-containers clearly differ from preforms for the production of blow-moulded co-layered containers, wherein the various layers of the container are not meant to delaminate, in the thickness of the layers. A bag-in-container is comprised of an outer structural envelope containing a flexible, collapsible bag. It follows that the outer layer of the container is substantially thicker than the inner bag. This same relationship can of course be found in the preform as well, which are characterized by an inner layer being substantially thinner than the outer layer. Moreover, in some cases, the preform already comprised vents which are never present in preforms for the production of co-layered containers (cf. EPA1356915).
One redundant problem with integrally blow-moulded bag-in-containers is the formation of the interface vents. Several solutions were proposed wherein the vent was formed after the bag-in-container was blow-moulded, as in U.S. Pat. Nos. 5,301,838, 5,407,629, JPA5213373, JPA8001761. This approach has of course the disadvantages that it involves an additional production step, and the danger of piercing the bag. Indeed these solutions have in common the formation of a hole normal to the outer container's wall and great accuracy is required not to degrade the inner layer's wall.
In EPA1356915 and U.S. Pat. No. 6,649,121, the preform is formed by injection moulding the outer layer first, followed by injection moulding the inner layer over the outer layer. During injection moulding of the layers, ventilation holes normal to the outer layer's wall are formed with protruding pins, which are flush with the inner surface of the thus obtained outer layer. The over-injected inner layer is not affected by the pins and this method solves the problem associated with the risk of damaging the inner bag during vents formation. The ventilation holes must be positioned close to the region of the container's mouth in an area of no or little stretching during the blow-moulding operation.
The venting holes described in EPA1356915 and U.S. Pat. No. 6,649,121, however, are not suitable for being connected to a source of pressurized gas to force delamination and squeezing of the inner bag. Furthermore, the inner and outer layers are little or not stretched in the region close to the container's mouth resulting in thicker and more rigid walls in this region than in the container's body. Consequently, a higher pressure would be required to delaminate the inner from the outer layers by blowing compressed air through the vents in a direction normal to the interface, as required in beg-in-containers for dispensing beverage like beer and sodas.
JPA10180853 discloses an integrally blow-moulded bag-in-container, wherein the preform consists of an assembly of an inner preform fitted into an outer preform such as to have a cavity transverse to the outer container's wall at a location very close to the preform assembly's mouth. Upon blow-moulding, said vent is maintained in the thus produced bag-in-container. It should be noted that the thickness of the preform's walls disclosed in JPA10180853 varies locally which can lead to serious processing and reproducibility problems of the final bag-in-container upon blow-moulding.
In order to optimize delamination of the inner and outer layers upon blowing pressurized gas into the vents, said vents should preferably run parallel to the interface between the two layers to provide a wedge effect. In the solutions proposed in the prior art relating to integrally blow-moulded bag-in-containers However, the vents run perpendicular to the interface and open to the atmosphere through a hole across, and normal to the outer container's wall, therefore providing no wedge effect and thus reducing the efficacy and reproducibility of the delamination of the inner bag from the outer container.
Bag-in-containers for beverage, like beer or sodas are usually positioned in a specially designed appliance comprising a dispensing passage to be connected to the mouth opening of the inner bag and a source of pressurized gas (generally air) to be connected to the vents opening(s). For reasons of compactness of the appliance, the vents design is restricted and should preferably open to the atmosphere at a location adjacent to the bag-in-container's mouth and oriented along the same axis as the latter, so as to allow all the piping to be bundled together. Such design follows the traditional beer keg interface in this regard, which is of course an advantage as it allows the replacement of a traditional keg by an integrally blow-moulded bag-in-container, without having to change the dispensing appliance.
It follows from the foregoing that there remains a need in the art for an integrally blow-moulded bag-in-container dispense package that allows optimization of the delamination of the inner bag from the outer container upon injection of a pressurized gas at the interface thereof and, at the same time, which can be used with the existing dispensing appliances.